1. Technical Field
The present invention relates to an AD converting apparatus, an analog-digital converting method, a test apparatus, a program, and a recording medium.
2. Related Art
An interleave AD converting apparatus with a high apparent sampling rate is known as an apparatus for converting an analog input signal into a digital output signal, as in, for example, Japanese Patent Application Publication No. 2005-347967. The interleave AD converting apparatus includes a plurality of AD converters and a combining section.
For example, the AD converters are supplied with sampling clocks that each differ by a prescribed phase. Each AD converter converts the input signal into digital data at timings according to the supplied sampling clock. The combining section arranges a single data sequence by arranging the plurality of data sequences output by the AD converters in an order corresponding to the respective sampling timings.
The AD converting apparatus disclosed in the above Publication compensates each signal output by an AD converter, according to the frequency characteristic of the corresponding AD converter. In this way, the AD converting apparatus 100 can accurately convert the analog input signal into a digital output signal, even if each AD converter has a different frequency characteristic.
However, due to various errors, the curve representing the relation between the amplitude of the input signal and the data value of the output signal after AD conversion deviates from the ideal line, e.g. a straight line. This characteristic of the curve expressing the relation between the amplitude of the input signal and the data value of the output signal deviating from the ideal line is known as a “non-linear characteristic.” If the AD converters have different non-linear characteristics, the output signal includes spurious components, which decreases the dynamic range of the interleave AD converting apparatus
A technique for compensating for the non-linear characteristics in the output signals of the AD converters has been considered. However, since each AD converter has a different non-linear characteristic, it is necessary to provide a non-linear characteristic compensating circuit for each AD converter. Providing each AD converter with a circuit that compensates for variation of the frequency characteristic and a circuit that compensates for the non-linear characteristic results in an undesirable increase in circuit size.